Tomato (Lycopersicon esculentum Mill.) fruits that do not meet grade standards for fresh market or processing are discarded. Such fruits may be damaged, diseased, too small, misshapen, etc. In Florida, for instance, cull tomatoes represent 20 to 40% of the tomato production, depending on the time of the year and weather events (Hoover et al., 1957; Sargent, 2008). This large amount of tomato wastage has always been a problem for tomato growers, and cull tomatoes are often scattered on vacant land and pastures or buried in the ground. Feeding them to livestock is a common way to get rid of them (Sargent, 2008).

Fresh tomatoes have the same drawbacks as other high-moisture feed ingredients: they are costly to transport, they spoil quickly, their nutritive value per kg of fresh matter is low and their bulkiness limits intake (Cotte, 2000).

Distribution

World tomato production was 152 million tons in 2009. The main tomato producers were China, the USA, India, Turkey, Egypt, Italy, Iran, Spain, Brazil and Mexico (75% of the world production) (FAO, 2011). More than a third of this production is grown for the processing industry, which makes tomatoes the world’s leading vegetable for processing (Tomato News, 2010). In 2007, tomato wastes were estimated at 11 million tons, including a little more than 4 million tons of tomato pomace (FAO, 2011; Tomato News, 2010).

The production of tomato by-products is seasonal and linked to the harvest period. Most of the product is available in the late warm-season and drying or ensiling is necessary for storage (Weiss et al., 1997). Tomato by-products are usually found in the vicinity of tomato processing plants.

Processes

Cull tomatoes are usually fed fresh.

A method for drying cull tomatoes and preparing them for livestock feeding was developed in the USA in the 1950s and 1960s: it consisted in cutting and pressing the fruit, drying the resulting pulp and then concentrating the pressed juice before adding half of it back into the pulp. The final mixture was then dried (Ammerman et al., 1965).

Environmental impact

Waste reduction

Feeding cull tomatoes to animals is one of the means to mitigate the environmental issues caused by the disposal of large amounts of fresh, easily spoiled fruits. Cull tomatoes should be disposed of as far away from production fields as possible to prevent contamination by pests and diseases (Schuster et al., 2006).

GM tomatoes

Genetically modified tomatoes containing a gene preventing the accumulation of polygalacturonase, an enzyme involved in the ripening process, were released in the mid-1990s, first as fresh fruits and then as tomato paste. These products were eventually commercial failures and, after an initial success, the GM tomato paste was removed from the market in 1999. In 2011, there were no GM tomatoes on the market (Bruening et al., 2000; GMO Compass, 2006).

Dried cull tomatoes produced by the process described in Processes contained more protein (22% DM) and (probably) less sugars because only half of the pulp is added back (Ammerman et al., 1963).

Potential constraints

Tomatine

Unripe tomatoes and the green parts of ripe tomatoes contain a solanine-like alkaloid (saponin) called tomatine, which may be toxic to insects, dogs, and to a lesser extent to herbivores causing diarrhoea, vomiting and intestinal irritation. Tomatine disappears as the tomato ripens (Milner et al., 2011; Straney, 1998).

Pesticide residues

Tomatoes are treated with numerous chemicals including insecticides, herbicides, etc. (Campos et al., 2007). Maximum limits for residues in food and feed are available in the Codex Alimentarius (Codex Alimentarius, 2011).

Ruminants

Cull tomatoes are a better ingredient than other tomato by-products but should not be given in large quantities.

Digestibility and degradability

Cull tomatoes are slightly more digestible that tomato pomace, as they contain all the highly digestible pulp and less fibre. The in sacco DM degradability and in vitro OM digestibility of fresh tomatoes were 58% and 63% respectively, providing a DE value of 10.8 MJ DE/kg DM. The in sacco degradability of protein is very low (20%), probably due to the high lignification of protein (almost half of tomato protein is linked to the ADF) (Ventura et al., 2009).

Cattle

When dumped in pastures for cattle feeding, cull tomatoes should be spread instead of dumped in a large pile to encourage consumption by cattle (Schuster et al., 2006). An early palatability trial found that dried cull tomatoes produced by the process described on the "Description" tab were as palatable as citrus pulp in dairy cattle (Hoover et al., 1957)

Dried cull tomatoes replacing citrus pulp as 10 to 30% of the concentrate in steer diets resulted in a similar performance than citrus pulp. In another study, steers fed diets with 70% or 100% dried cull tomatoes, digestibility decreased slightly when they were fed alone. No problems were encountered, although the steers seemed to be getting insufficient fibre at the 100% level (Ammerman et al., 1963).

Sheep

In lambs, the protein of dried cull tomatoes fed at 33% of the diet was less digestible and of lower biological value than that of soybean meal (Ammerman et al., 1963).

Like other tomato by-products, cull tomatoes are fibrous and only limited amounts should be fed to poultry. Dried cull tomatoes (see Processes) satisfactorily replaced alfalfa meal as 3% of the diet for broilers. However, carotenoid pigmentation in skins and shanks was reduced (Ammerman et al., 1965).